In the electronics industry it is typically necessary to locate many different electronic components with respect to an underlying substrate or printed circuit board and to assemble those components to the substrate. With the introduction of the printed circuit board, the assembly of electrical components to that board was typically done by hand. Consequently, labor costs were high. The first automation which was accomplished in the industry was done with dedicated assembly equipment which was used for the assembly of components to a particularly sized and shaped printed circuit board. In this early dedicated assembly equipment circuit boards of a given size and shape were loaded into a magazine and thereafter fed from that magazine by a conveying means to and from an assembly station. Since the dedicated assembly equipment was used for the assembly of a given electronic circuit, automation made economic sense only when the particular circuit being assembled was a high volume item. Moreover, such dedicated assembly equipment was characterized by high capitalization costs.
The electronic industry is characterized by short product life spans or, at least, by product life spans having varying magnitude. Because of the high capitalization costs of dedicated assembly equipment, and because of short product life spans, the dedicated assembly equipment was not particularly useful for the assembly of electronic components in small lots.
Because of these difficulties with dedicated electronic assembly equipment, variable, programmable assembly techniques are now being widely utilized for the placement and assembly of electronic components on printed circuit boards. With these programmable assembly techniques, robotic means are utilized for selecting individual electronic components from a storage area and for transporting those selected components to an assembly station. At the assembly station, the robotic means properly locates the components with respect to the printed circuit board. In the parent applications to the present application improved end effectors for such a robotic means are disclosed. The end effectors described grasp a component to be assembled. The end effectors are fixed to a carriage which locates the end effector with respect to an X-Y plane and, consequently, the components are located with respect to a substrate in that plane. The end effectors are also movable in a Z direction perpendicular to the plane. After the end effector grasps the selected electronic component from a storage location and the carriage moves the end effector from the storage location to the printed circuit board, the end effector moves downwardly in the Z direction and precisely locates the component on the printed circuit board.
Because the robotic means of the parent applications is programmable, various circuits may be assembled by a single programmable assembly means, and the high capital cost of dedicated assembly equipment is avoided as well.
Despite their success, a number of problems remain with prior art programmable assembly techniques utilizing robotic means for the placement of electronic circuit components on substrates or printed circuit boards. One of these problems is the difficulty of conveying unassembled printed circuit boards to the work station for assembly purposes. This problem has, to a certain extent, been solved by the provision of a linear conveying means which directs the unassembled printed circuit boards to the assembly or work station. A further problem is presented, however, by virtue of the fact that printed circuit boards typically are provided in a wide variety of shapes and sizes and, therefore, the linear conveying means for transporting those circuit boards to the assembly station must be capable of accommodating such differing shapes and sizes.
Another problem presented with prior art programmable assembly techniques is that at the assembly station, typical printed circuit boards require the placement of a large number of differing components with respect to a single circuit board. Space constraints, however, limit the number of differing components which may be assembled on a given substrate or circuit board with a given robotic assembly machine. To solve this problem, it has been suggested to employ a plurality of programmable robotic assembly machines with each programmable assembly machine being used for assembling a subset of the total number of components to be assembled on a given printed circuit board. After a given circuit is partially assembled with a first assembly machine the partially assembled circuit board is transferred to a second programmable assembly machine for further assembly. A given circuit board, therefore, may pass numerous programmable assembly stations until the final assembly has been completed. In the past, no suitable means has been provided for the conveyance of partially assembled printed circuit boards from one robotic assembly station to the next where the size and shape of the substrates or circuit boards varies one from another.
In one arrangement which has been suggested a number of programmable assembly machines are configured in an assembly line, with each assembly machine being utilized for fixing a certain subset of components to a particular printed circuit board. A linear conveyor transports a circuit board along the assembly line from one assembly machine to the next. With such an approach, the linear conveyor must be adjusted to accommodate a particular circuit board size and shape. When it is desired to assemble a circuit board having a different size and shape, the linear conveying means of the entire assembly line must be adjusted from the first through the last assembly station to accommodate that differing size and shape. Changeover or set up time from one conveying means configuration to another configuration causes substantial down time and lowers productivity.
It would be particularly desirable to provide a substrate transport means for conveying printed circuit boards and other substrates of varying sizes from one programmable assembly machine to the next along an assembly line. It would be further desirable to provide for the programmable assembly of electronic components to a wide variety of changing circuit board sizes and configurations. It would be still further desirable to provide a programmable substrate transport means which may be used for not only printed circuit board assembly but also for silk screening and for assembly of hybrid planar circuits. These and other objectives are achieved by the provision of the programmable substrate transport mechanism of the present invention.
These and other objects of the present invention are accomplished by means of an apparatus for the assembly of electronic components which preferably comprises a plurality of assembly modules. Each assembly module includes an assembly station to which substrates are directed and at which electronic components are assembled. A programmable linear conveyor directs substrates to each assembly station and a control means adjusts the linear conveyor in accordance with the predetermined width of each substrate and varies the entry width to that conveyor in accordance with the substrate width.
In accordance with the preferred embodiment, at each assembly station, a programmable means for positioning components with respect to a substrate located thereat is provided. This programmable means preferably comprises a carriage and an end effector coupled to the carriage. The carriage grossly positions components with respect to the substrate, and the end effector precisely positions components with respect to the substrate.
In accordance with an important aspect of the present invention, each assembly module includes a conveyor having a first and second movable belt traveling in parallel paths. The aforementioned control means controls the speed of the first and second belts so as to convey substrates to the assembly station. Means are provided for adjusting the distance between the paths in accordance with the predetermined width of each substrate to which assembly is accomplished.